1. Field of the Invention
The present invention relates to a vehicle lamp provided with a projector-type lamp unit.
2. Related Art
Generally, a vehicle lamp is designed as a structure in which a lamp unit, having an optical axis extending in a vehicle longitudinal direction, is accommodated within a lamp room including a lamp body and a light-transmissive cover attached to a front opening of the lamp body. An example of the lamp unit is the projector-type lamp unit disclosed in e.g. JP-A-63-314701.
In the projector-type lamp unit, a projector lens is arranged on an optical axis, and a light source is arranged on a rear side of a rear focal point of the projector lens. In addition, the light emitted from the light source is reflected near the optical axis by a reflector. In this case, a planoconvex lens is generally employed as the projector lens. The planoconvex lens is convex in the front face and planar in the rear end face. In the projector lens, a line connecting the upper and lower ends of the rear end face, which is a plane opposite to the reflector, is arranged in parallel to a vertical line.
However, the conventional type headlamp presents the following problems. Namely, in a light distribution for passing (that is, a lower beam distribution), substantially half of the quantity of light is shielded by a shade so that the efficiency of the light distribution is low. In addition, since only the projector lens is seen when the vehicle lamp is mounted on a vehicle, the design does not appear new any more.
Thus, in the projector-type lamp unit disclosed in e.g. JP-A-2003-123519 and JP-B-07-031921, by making the front face of the projector lens convex and inclining the line connecting the upper and lower ends of the rear end face from the vertical line, the entire light is oriented downward by the prism operation of the projector lens so that the shielded quantity of light by the shade is reduced to improve brightness and the design appears new.
However, in the vehicle lamp with the projector lens inclined as described above, when the conventional shade and reflector are attached, a horizontal cut-line suited to a light distribution regulation cannot be formed. Specifically, in a conventional shade 1, as seen from FIG. 15(a), the upper edge is composed of horizontal straight-line segments 1a and 1b when seen from the direction of the optical axis of the projector lens. This is intended to provide a linear cut off line corresponding to the imaging characteristic of the projector lens. However, if the shade 1 is adopted for the inclined projector lens 1, as seen in FIG. 15(b), the cut off line 3 is curved downward with diffusion in a right/left direction. This led to a problem that regions 5R, 5L with reduced distant visibility are formed horizontally. Further, a conventional reflector 7 is formed of a curve that reflects the light emitted from a light source 13 in a nearly horizontal direction (direction of arrow 15) in a minute area on a horizontal section 11 passing the optical axis Ax of the projector lens 9 as seen in FIG. 16(a). This is intended to diffuse light in the horizontal direction according to the imaging characteristic of the projector lens 9. However, if the conventional reflector 7 is adopted for the inclined projector lens 9, the horizontally diffused light is curved downward as it diffuses. This also led to a problem that regions 17R, 17L with reduced distant visibility are formed horizontally, as shown in FIG. 16(b).